The present invention relates generally to a multiple-core optical fiber arrangement with simultaneous independent single-mode or multimode and multimode transmission capabilities, and more particularly to such an optical fiber with a concentric core construction as provided by an inner single-mode or multimode optical fiber formed of a core encased in a cladding of a lower index or refraction and an outer multimode optical fiber provided by an additional cladding of yet a lower index of refraction concentrically disposed about the casing of the inner optical fiber whereby the cladding of the inner optical fiber functions as the core of the outer multimode optical fiber.
Optical fibers have been successfully utilized in sensor applications for detecting and measuring various physical parameters such as temperature, strain, moisture content, and the like. The optical fibers previously used for the detection and the measurement of such physical parameters were limited to the transmission of sensor signals with either a signal-mode or a multimode propagation. Thus, the multiplexing of various types of sensors such as highly sensitive, interferometric-based sensors with less sensitive, amplitude-based sensors on the same optical fiber has not been possible.
Optical fibers have also been increasingly used in signal transmission applications such as in telecommunications where the light signals are transmitted over long distances by employing single-mode optical fibers over shorter distances by using multimode optical fibers. While the use of single-mode and multimode optical fibers in the telecommunication field are of significance importance, the signals being transmitted through the previously known optical fibers can be surreptitiously extracted so as to compromise the security of the telecommunications.